1. Field of the invention
The object of the invention is a walking beam pumping unit for operating an immersed piston pump, primarily an oil well pump.
2. Description of the prior art
As is known, oil well pumps are operated through the intermediary of a long line of sucker rods, movement of which in the transverse direction is extremely limited. As a result, the reciprocating drive member must follow a trajectory differing only very slightly from a straight line at the point where it is coupled to the upper end of the sucker rod line.
In conventional pumping units a walking beam is coupled at one end to a crankshaft-crank system driven by a motor which causes it to rock about a fixed horizontal axis. At its opposite end the walking beam is fitted with a head having a circular arc shaped free end surface. Formed in this curved surface are grooves in which are mounted cables which terminate at the upper end of the sucker rod line. These cables are always tangential to the curved surface and are always contained within the same vertical plane. As a result there is relatively high acceleration and deceleration at the ends of travel and, for a given motor torque, a relatively restricted length of travel; furthermore, the cables are subject to wear, requiring periodic inspection and replacement.
A principal objective of the invention is to provide a walking beam mechanism which, driven by a conventional motor, makes it possible to obtain a significantly greater travel for the same motor torque along a trajectory which is sufficiently rectilinear to be acceptable, with lower accelerations and decelerations than in conventional pumping units.
Another objective of the invention is to eliminate any cables between the walking beam and the sucker rod line, through the use of a mechanism of the above-mentioned type.